The prior art discloses forced convection furnaces for heating of glass sheets in preparation for processing such as forming, tempering, heat strengthening, annealing, and coating, etc. Such prior art forced convection furnaces for heating glass sheets are disclosed by the United States Patents of Kenneth R. Kormanyos: U.S. Pat. Nos. 5,669,954; 5,672,191; 5,735,924; 5,762,677; and 5,792,232. In those Kormanyos patents, the glass sheets are conveyed on a roll conveyor during the heating which is performed by lower and upper sets of hot gas distributors that supply pressurized hot gas flows to the lower and upper surfaces of the conveyed glass sheets. An associated lower hot gas distributor is located between each pair of adjacent conveyor rolls, such that the spent quenching gas must flow downwardly between the conveyor rolls and the hot gas distributor. Furthermore, any broken glass that is lodged between the conveyor rolls and the lower hot gas distributors must be removed before commencing further heating of the glass sheets.
An object of the present invention is to provide an improved method for heating glass sheets.
In carrying out the above object, the method for heating glass sheets is performed by conveying the glass sheets by a roll conveyor on horizontal conveyor rolls spaced along a direction of conveyance within a housing heating chamber. Hot gas flow is supplied from below the roll conveyor upwardly adjacent alternate conveyor rolls through a pair of banks of nozzles associated with each alternate conveyor roll for upward flow both upstream and downstream of each alternate conveyor roll along the direction of conveyance to provide heating from below of the conveyed glass sheets. Hot gas flow is also supplied from above the conveyor downwardly to provide heating from above of the conveyed glass sheets.
In the preferred practice of the method, the glass sheets are heated by hot gas flows that are supplied upwardly and downwardly from aligned banks of nozzles to provide aligned lower and upper locations of hot gas impingement with the glass sheets being heated. The upwardly and downwardly supplied hot gas flows are supplied through lower and upper hot gas distributors that have a dimension along the direction of conveyance equal to the diameter of the conveyor rolls. Furthermore, the upwardly and downwardly supplied hot gas flows are supplied through lower and upper hot gas distributors that are formed from sheet metal.
The objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.